langchain breaking changes

1.3.8

2 breaking changes, first published June 12, 2026.

• Signature changed langchain.agents.create_agent
  Was def create_agent(model: str | BaseChatModel, tools: Sequence[BaseTool | Callable[..., Any] | dict[str, Any]] | None = None, *, system_prompt: str | SystemMessage | None = None, middleware: Sequence[AgentMiddleware[StateT_co, ContextT]]... pypi.org
• Signature changed langchain.agents.middleware.ModelCallResult
  Was ModelCallResult: TypeAlias; now ModelCallResult. pypi.org

1.3.7

4 breaking changes, first published June 10, 2026.

• Signature changed langchain.agents.middleware.dynamic_prompt
  Was def dynamic_prompt(func: _CallableReturningSystemMessage[StateT, ContextT] | None = None) -> Callable[[_CallableReturningSystemMessage[StateT, ContextT]], AgentMiddleware[StateT, ContextT]] | AgentMiddleware[StateT, ContextT]; now def... pypi.org
• Signature changed langchain.agents.middleware.wrap_model_call
  Was def wrap_model_call(func: _CallableReturningModelResponse[StateT, ContextT, ResponseT] | None = None, *, state_schema: type[StateT] | None = None, tools: list[BaseTool] | None = None, name: str | None = None) ->... pypi.org
• Signature changed langchain.agents.structured_output.OutputToolBinding.parse
  Was def parse(self, tool_args: dict[str, Any]) -> SchemaT; now def parse(self, tool_args: dict[str, Any]) -> SchemaT | dict[str, Any]. pypi.org
• Signature changed langchain.agents.structured_output.ProviderStrategyBinding.parse
  Was def parse(self, response: AIMessage) -> SchemaT; now def parse(self, response: AIMessage) -> SchemaT | dict[str, Any]. pypi.org

1.3.6

2 breaking changes, first published June 10, 2026.

• Signature changed langchain.agents.middleware.SummarizationMiddleware.__init__
  Was def __init__(self, model: str | BaseChatModel, *, trigger: ContextSize | list[ContextSize] | None = None, keep: ContextSize = ('messages', _DEFAULT_MESSAGES_TO_KEEP), token_counter: TokenCounter = count_tokens_approximately... pypi.org
• Signature changed langchain.agents.middleware.SummarizationMiddleware.trigger
  Was trigger: ContextSize | list[ContextSize] | None; now trigger: ContextSize | TriggerClause | list[ContextSize | TriggerClause] | None. pypi.org

1.3.2

1 breaking change, first published May 26, 2026.

• Signature changed langchain.agents.create_agent
  Was def create_agent(model: str | BaseChatModel, tools: Sequence[BaseTool | Callable[..., Any] | dict[str, Any]] | None = None, *, system_prompt: str | SystemMessage | None = None, middleware: Sequence[AgentMiddleware[StateT_co, ContextT]]... pypi.org

1.3.0

1 breaking change, first published May 12, 2026.

• Signature changed langchain.agents.create_agent
  Was def create_agent(model: str | BaseChatModel, tools: Sequence[BaseTool | Callable[..., Any] | dict[str, Any]] | None = None, *, system_prompt: str | SystemMessage | None = None, middleware: Sequence[AgentMiddleware[StateT_co, ContextT]]... pypi.org

1.2.14

1 breaking change, first published March 31, 2026.

• Removed langchain.agents.middleware.todo.InjectedToolCallId
  langchain.agents.middleware.todo.InjectedToolCallId was removed in langchain 1.2.14 pypi.org

Check your code

These are the changes. To see which of them reach your code, scan a public repository, or have your coding agent call check_code with your manifest or lockfile over MCP. The API reads every change in every version, not only the newest. On Team and up, a fix pull request opens for the changes that reach a connected repository. Nothing merges or deploys.